This Lumetron Colorimeter Model 400-A was introduced in the 1940s by the Photovolt Corporation in New York, NY.
Housed in a wooden box, the electrically-powered instrument includes two filter holders, a test tube carrier, a meter, and detailed instructions inside the lid. The instrument’s six glass filters cover the color spectrum—red, yellow-green, blue, orange, blue-green, and violet. The test tube carrier and the filter holders have metal knobs for ease of removal and the carrier has two holes for tubes with metal plaques noting “BLANK” and “SAMPLE” affixed above and below the holes respectively.